If you go to Japan, a daily activity that you will face is the etiquette at mealtime. First of all, if you don’t know how to use chopsticks, I recommend that you do it, because they are the quintessential utensil.
Before they start eating, people often say 「い た だ き ま す」(itadakimasu) and at the end of eating 「ご 馳 走 様」（ご ち そ う さ ま 、gochisousama). They are ways of saying “enjoy your meal” and “thanks for the food” (not literally, but the meaning of the translation would be that). It is common in Japanese restaurants to serve dishes in the center of the table and share them. When taking a bite, do it with the opposite end of the one you use to eat.
Some things that are considered rude they are: blowing your nose, talking about bathroom or other unpleasant things at the table, burping, leaving a plate unfinished, and pouring yourself extra soy sauce.
The Japanese are very superstitious. Many think it is from bad luck stick chopsticks into rice or pass a sandwich from one person to another using chopsticks. They both have to do with funeral rites. Rice dishes are usually offered with sticks stuck to the deceased, and when the body of the deceased is cremated the bones are passed from one relative to another by means of the chopsticks. Avoid doing either of the two things at the table.
Refering to drink, it is not well seen that you serve yourself in your own glass. Serve the other first if you see that the glass is almost empty and wait for them to serve you. In refined restaurants it does not look good for people to drink too much. In other more traditional restaurants it is very common to see workers or students taken. Of course, avoid disturbing other customers. Finally, no one starts drinking until everyone has a glass poured and says 「乾杯!」（か ん ぱ い！ kampai!).